Immune system

We often automatically retreat to bed when we have a cold or sore throat, instinctively perceiving that sleep helps us heal. Growing evidence suggests this is not mere wishful thinking but scientific fact. The best evidence for sleep's impact on the immune system comes from a recent study showing that the effectiveness of flu vaccinations is severely delayed in individuals who are sleep deprived. Flu shots were administered to men who had been restricted to just four hours of sleep per night for four straight nights and to those who had slept normally. Ten days after vaccination, those in the sleep deprived group had a substantially lower immune response compared with those who got adequate sleep, producing less than half as many flu-fighting antibodies. Cytokines, chemicals our immune systems use to help fight an infection, also are powerful sleep-inducers. This suggests that sleep may help the body conserve energy and other resources it needs to mount an immune response and fight disease.